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Apparently its quite common for it to break the connection on the blend door itself. So I've repaired it with superglue and put a new blend door motor, but it travels too far and has broken off again.
Do we know what the motor uses to determine its position? I have read that some use the resistance from the door being shut for it to know its in the closed position and thus know where it is and stop turning.
Any input is much appreciated, I've also read the a damaged harness can cause it to travel too far. The motor, with repeated Climate control on and off, will try to turn all the way around, in short amounts.
(this is the same issue and repair as posted by someone on youtube, I wonder if his broke off again)
Do we know what the motor uses to determine its position? I have read that some use the resistance from the door being shut for it to know its in the closed position and thus know where it is and stop turning.
Good question, wish I had a clear answer for you. The actuators have an internal potentiometer for position feedback. See figure 06.1 in the wiring diagram. For each actuator, the two wires shown at the left drive the motor. The three wires to the right are for position feedback:
You'd think there would be a calibration procedures, but I couldn't find one. The replacement procedure in the service manual just says to install it, implying no calibration is required. See page 2701 here:
Does the control module somehow do a self-calibration, perhaps looking at current draw to indicate end of travel like you were thinking? It's possible, but that is strictly a guess.
I was going to suggest replacing the actuator, as maybe it's not really calibrated to the vehicle per se. The manual makes it seem the actuator is plug 'n play, and the tolerances aren't all that critical. But I see you have already replaced the actuator.
When the door reaches full travel, does it seem to be fully closed? Maybe something is limiting its travel?
How far does the actuator overtravel? If just a smidge, I wonder if the attach point is just a weak spot prone to breakage. Instead of just repairing the broken bit, could you reinforce it with something stronger?
Is there any play at the actuator attach bolts? Could you enlarge the holes and reposition the actuator slightly to reduce tension on the fragile attach point for the linkage? Or if not possible, could you fabricate a slightly longer piece of linkage to compensate?
If none of this is possible, I suppose you could always disconnect the linkage and secure the door in the fresh air position. AFAIK, recirc is only used for quicker cooling on a hot day, or if you need to briefly block external air such as if passing through a dust cloud.
Thanks for getting in touch again Thumbs up
The first post you have attached does suggest it should know via its internal circuitry, I had the old one open as it had travelled too far and needed putting back into its proper position. Whilst in there I noticed there was an electrical contact arc that was about half the travel of the main gear (180degrees) and had contacts on the gear that brushed against it (the internal potentiometer).
Unfortunately the new motor presents the exact same behaviour, travelling so far that it reaches the point of hitting the plastic casing of the blower and related ducting above, I would imagine without that obstruction it would continue full circle in short bouts of movement. On the potentiometer the brush contacts travel past the arc and are rubbing on plastic of the circuit board, so I can only wonder what readings its feeding back into the system.
After the initial repair it did function as normal opening and closing as it should on the recirc button for a while (a dozen or so pushes to open and close the blend door).
Although it was a bit concerning how firmly it was holding it shut. I eventually travelled too far and broke off the repair, or it broke it off allowing it to travel too far. Which came first, the chicken or egg!
After that initial travel that is too far it no longer responds to the recirc button and sporadically travels a little further in that direction when the ignition is turned on and off, until it hits the plastic above.
I did consider sorting out a longer piece of metal so it wouldn't pull it past the point of where it breaks, but with it continuing to travel it would leave me at the stage where it is jammed against the equipment above. I also considered making up a small aluminium bracket and riveting it to the blend door, but I would imagine the actuator would probably have the power to rip it off the door and do more damage to the blend door, unless of cause the resistance created by being held shut is indeed what tells it it is fully closed (perhaps the repair just wasn't strong enough to work in this fashion?).
I'm thinking to reset it back to the proper position and then use the recirc button but rather than connect it to the door, put my hand in the way to simulate the door being shut, but in a different position to where the door would cause it, in essence to test whether the resistance to movement is what tells it to stop.
Hopefully there's an answer as I do use the recirc button fairly often, especially when there's a smoking diesel in front!
Talking
Just had a go at stopping it in random positions manually and it did stop where it meet resistance.
I've reattached it to the door (the superglue repair has had 24hours to cure), so hopefully it will hold this time, otherwise it seems an aluminium bracket and rivets may be in order!
It works as it should currently, but how long my repair holds up is anyone's guess. Hopefully this is the issue and how it works and I hope it helps others.
Is the replacement actuator new or used? If used, consider the actuator spends nearly all its life in the fresh air position. Vibration may have worn a dead spot in the potentiometer at the same spot as the original one.
That's the original one, as I had it out anyway I opened it up and reset it to test it. As it worked as tested, I removed the new one and fitted the old one back in the car and it seems to work, whether the repair holds though...
I should probably return the new one
What is the recent history of your car? Have you owned it for years, lovingly maintained it in original condition, and this problem appeared out of the blue one day? Or has the car just been dragged from the proverbial field (we literally had one recently), you found a rabid possum living inside the ductwork, and you've haven't even driven it yet? Something in between? Any details about when this problem started will be really helpful.
Any chance the linkage was separated for some time but you didn't realize it? Any signs that somebody else had worked in this area before you?
Did you check the actuator in a parts catalog? Or did you just order another one by the existing part number? Just wondering if a previous owner set you up by installing the wrong actuator.
If you're positive the actuator is correct, could a gear have jumped a tooth? Or if the output arm is splined, could it have been assembled incorrectly?
Does the actuator presently stop (linkage disconnected) in the same position at each end of travel? If consistent, rather than try to figure out why it's not right, could you shorten the arm to reduce the travel? This might be an easier option.
Its got quite a nice history, the original owner used to take it to Jaguar themselves for everything. When it came to sorting out the surge the owner gave up and that's when it came into my possession. I've always felt guilty that it has a complete service history that ends with me as I do the work myself. It is in lovely condition generally, I had the torque convertor reconditioned a couple of months ago to get rid of the hunting issue when going up a slight gradient at around 30mph. The surge it was getting was caused by an air leak on the engine, it was a rubber vacuum line connector that simply needed replacing (Jaguar quoted an oil change and potential new gearbox to the original owner).
To be fair the linkage may have been broken for a couple of years as I haven't had the glovebox out since about two years ago, and the broken off parts were still there when I opened it up the other day, it would have otherwise have been lost. I'm not 100% sure if the face vents blow at correct temperature as I haven't used it since doing the repair last night, but before it broken off the first repair they seemed to be behaving as normal (although I cant see how that might affect it).
There was no evidence that anyone had been in there before, but that doesn't mean too much as I imagine Jaguar are very clean and tidy with their work.
When finding the new part I went by exploded parts diagrams on the sngbarrett website so I know it is the correct, I now have a spare!
When it went wrong it would travel past the arc contacts in one long motion (I'm thinking it was waiting for the resistance from the door being shut) . At that point the contacts are no longer in contact and the only movement is sporadic short ones, about 15degrees when the ignition is on and off. I would imagine that is from the lack of any electrical feedback. The actuator only stops when there is resistance, both the new and old continue to travel until the contacts are broken in the potentiometer. I am thinking to add a way of blocking the arm on the motor rather than rely on pulling on the door shut, but I'm not sure where that would go, perhaps even to block the last tooth spacing when it gets into position so that stops it. It all depends on how well my repair holds up. The true fix would be a new blend door, I haven't looked into it yet, but I would imagine they are not easy to swap out.
Looking at where it has broken and if it does rely on the force of the door being shut I would recommend to everyone to superglue a penny washer there to add strength, rather than wait for the blend door to get damaged. (If this is the way it functions of course)
The actuator only stops when there is resistance, both the new and old continue to travel until the contacts are broken in the potentiometer. I am thinking to add a way of blocking the arm on the motor rather than rely on pulling on the door shut...
That seems like the way to go. Does the actuator look like this?:
I wasn't sure what was what at SNGBarrett, but this eBay item looked like the one in the video at the start of this thread. If indeed the physical resistance from the end of travel is what "self-calibrates" the actuator, I like the idea to add an external block to stop the actuator arm. A small block of aluminum or stiff plastic would work, secured from inside with a pair of screws. This would take the stress off the door itself. You could test it by connecting the wiring, without having to bolt the actuator in place.
here's a picture of the inside where you can see the arc/semicircle contact set up beneath the gear (hopefully it hasnt uploaded it the ridiculous size the preview shows)
One more thought, if you plan to rig up a physical stop on the actuator. When you test it, be ready to quickly undo the wire connector in case the actuator keeps trying to drive. It looks like all actuators share power via a common fuse feeding the control module. This fuse may not open as quickly as one might hope.
that's a very good call! Thanks for mentioning it, I hadn't even considered the source of its power, I've already had that game with the climate control when I didn't replace the DCCV in time.
Recirculation Blend door Travelling too far
